Figure 13-3.

Hematopoietic Cell Morphology, Feline (Erythroid and Granulocyte Lineages) and Canine (Monocyte Lineage) Blood Smears and Bone Marrow Aspirates.

As erythroid cells mature from a rubriblast to a mature erythrocyte, their nuclei become smaller and more condensed. The nucleus is eventually extruded to form a polychromatophil. Erythroid cells also become less basophilic and more eosinophilic as more hemoglobin is produced and as RNA-rich organelles are lost during maturation. (Hemoglobin stains eosinophilic, and RNA stains basophilic with routine Romanowsky's stains.) As granulocytes (e.g., neutrophils, eosinophils, and basophils) mature from a myeloblast to their mature forms, their nuclei become dense and segmented. Granulocytes acquire their secondary or specific granules during the myelocyte stage and can be morphologically differentiated starting at this stage. Neutrophils have neutral-staining secondary granules, eosinophil secondary granules have an affinity for acidic or eosin dyes, and basophil secondary granules have an affinity for basic dyes. Monoblasts differentiate into promonocytes with ruffled nuclear boarders and then into monocytes. (Courtesy Dr. K.M. Boes, College of Veterinary Medicine, Virginia Polytechnic Institute and State University; and Dr. J.F. Zachary, College of Veterinary Medicine, University of Illinois.)